Black-throated Blue Warbler (Female) in Pennsylvania.

The black-throated blue warbler (Setophaga caerulescens) is a small passerine bird of the New World warbler family.

Black-throated Blue Warbler (Female) in Pennsylvania.

A uniquely colored, midnight-blue bird of tangled under-stories, the male Black-throated Blue Warbler sings a relaxed, buzzy I-am-so-la-zee on warm summer days in Eastern hardwood forests. He’s aptly named, with a midnight blue back, sharp white belly, and black throat. The olive-brown females, while not as dramatically marked as the males, have a unique white square on the wing that readily separates them from other female warblers. This warbler breeds in the East and spends the winter in the Caribbean. [All About Birds]

Black-throated Blue Warbler (Female)

Black-throated Blue Warbler Facts [All About Birds]

• Male and female Black-throated Blue Warblers look so different that they were originally described as two different species.
• On the wintering grounds, males and females use slightly different habitats. The male is most common in the forest at lower to middle elevations, while the female uses shrubbier habitat at higher elevations.
• In the Dominican Republic, Black-throated Blue Warblers take advantage of a sweet treat created by insects harvesting tree sap. These insects feed on tree sap and excrete drops of sweet sap or “honeydew” from their back ends that the warblers drink up.
• The oldest Black-throated Blue Warbler was a female, and at least 9 years, 8 months old. She was banded in New Jersey in 1975 and shot in Panama in 1985.